The present invention relates to a method and equipment for manufacturing a semiconductor device wherein treatments to be performed under different temperature conditions and in different treatment atmospheres are successively performed such that the epitaxial growth of semiconductor layers of different compositions is successively performed at different temperatures or that a heat treatment is performed during the epitaxial growth of the semiconductor layers.
In manufacturing a semiconductor device, in particular, a semiconductor light emitting device, treatments are continuously performed such that the epitaxial growth of semiconductor layers of different compositions is performed under different temperature conditions or that a heat treatment is performed during the lamination of the semiconductor layers. For example, a blue semiconductor light emitting device using gallium nitride (GaN) based compound semiconductor layers is manufactured in the following manner:
First, a sapphire substrate is placed in a pretreatment chamber to perform a pretreatment at approximately 1100.degree. C. in an atmosphere of hydrogen. Then, after the temperature is decreased to nearly room temperature, the substrate is moved from the pretreatment chamber into a metal-organic chemical vapor deposition (MOCVD) apparatus and a reaction gas is supplied into the apparatus to grow a buffer layer of GaN at approximately 500.degree. C. Then, at a high temperature of 1000.degree. C. or higher, the epitaxial growth of a clad layer and an active layer of GaN based compound semiconductor are successively performed. Then, the substrate is taken out from the MOCVD apparatus and placed in a reactor for heat treatment to perform annealing at approximately 700.degree. C. in an atmosphere of nitrogen.
As described above, when the substrate is moved from the pretreatment chamber into the MOCVD apparatus and from the MOCVD apparatus into the heat treatment chamber, it is necessary to decrease the temperature to nearly room temperature before taking out the substrate and to increase the temperature again after the substrate is placed in another treatment apparatus. For this reason, a waiting time of approximately 30 to 90 minutes is necessary to move the substrate from one apparatus into another at each process. Moreover, even between the treatments performed in the same MOCVD apparatus, it is necessary to increase the temperature within the apparatus from approximately 500.degree. C. to approximately 1000.degree. C. between the growth of the buffer layer to be performed at a low temperature and the epitaxial growth of semiconductor layers forming a light emitting portion to be performed at a high temperature. To change the temperature, approximately 5 to 10 minutes are necessary, so that a long waiting time is necessary between the processes. This increases the number of man-hours and decreases the availability ratio of the expensive equipment.
Additionally, in the epitaxial growth of the semiconductor layers, when the growth in the MOCVD apparatus and the growth in a molecular-beam epitaxy (MBE) apparatus are continuously performed, it is necessary to take the substrate out of one apparatus into the air to move it into the other apparatus, so that not only the temperature is necessarily decreased to nearly room temperature but also the surface of the substrate is oxidized when the substrate is taken out into the air during the epitaxial growth of the semiconductor layers. As a result, high-quality semiconductor layers cannot be grown.
On the other hand, to produce an apparatus which serves as both the MOCVD apparatus and the MBE apparatus, it is necessary to provide the apparatus with all the facilities of the MOCVD and MBE apparatuses and to take measures against corrosion due to an organometallic compound gas. This results in an expensive apparatus. In the case where the treatments are performed only in the MOCVD apparatus, when the number of MOCVD apparatus is increased to perform a mass production, it is necessary to design all of them to be capable of enduring a treatment performed at the highest temperature and of enduring all kinds of gases used for the treatments, so that it is necessary to prepare a plurality of expensive apparatuses.